Thermostatic mixing valves enable hot and cold fluids, typically water, to be accurately mixed so as to deliver fluid at a desired temperature to the valve outlet. One form of thermostatic mixing valves adopts a “T” pattern in which the hot and cold water enters through inlets in the arms of the “T” and the mixed water exits through an outlet in the base of the “T”. Another form of thermostatic mixing valve adopts an “L” pattern in which the hot and cold fluid inlets are orientated at right angles to each other.
Thermostatic mixing valves include hot and cold seats for respectively isolating the flow of hot and cold fluids through the valve. Such seats are typically provided by a hard edge of a piston pressing firmly against a flat face of the valve body to thereby prevent fluid flow. In one form of “T” pattern mixing valves, both the hot and cold seats have been provided in this manner. However, the design of such mixing valves has been complicated by the need to provide a mechanism for allowing for any continued expansion of the thermostatic element after the flow of hot and cold fluids is adjusted. This problem has been addressed by including a spring arrangement adjacent to the leading end of the thermostatic valve (i.e. in the hot seat). The inclusion of such an arrangement requires an extra opening to be formed in the valve body and also increases the part and production costs for the valve.
Another problem with such mixing valves is that to enable adjustment of the set temperature of the mixed water exiting the outlet (and thereby the rest position of the thermostatic element), additional constructional features or components have to be provided. This inevitably increases the cost of the mixing valve.
The present invention seeks to provide an improved thermostatic mixing valve that addresses at least some of the above mentioned problems.